Multi-piece solid golf ball

摘要

A multi-piece solid golf ball composed of a solid core having an inner core layer and an outer core layer encased by a cover including at least an inner cover layer and an outer cover layer. The inner core layer has a JIS-C cross-sectional hardness of from 60 to 83 at any single point on a cross-section, and has a cross-sectional hardness difference between any two points on the cross-section of within ±5. The ball has specific relationships between the hardness of the inner core layer 1 mm inside a boundary between the inner core layer and the outer core layer, the hardness of the outer core layer 1 mm outside the boundary, and the surface hardness of the outer core layer. And, the outer cover layer has the specific Shore D hardness, which is lower than that of the inner cover layer.

主权项

1. A multi-piece solid golf ball comprising a solid core encased by a cover of two or more layers, which solid core has an inner core layer and an outer core layer, and cover has an inner cover layer and an outer cover layer, wherein the inner core layer is formed primarily of a thermoplastic resin, has a diameter of from 21 to 38 mm, has a JIS-C cross-sectional hardness of from 60 to 83 at any single point on a cross-section obtained by cutting the inner core layer in half, and has a cross-sectional hardness difference between any two points on the cross-section of within ±5; the outer core layer is formed of a rubber composition made primarily of polybutadiene rubber; the core of the inner core layer and the outer core layer combined has a diameter of from 35 to 42 mm; and, letting (b) represent the JIS-C cross-sectional hardness of the inner core layer 1 mm inside a boundary between the inner core layer and the outer core layer, (c) represent the JIS-C cross-sectional hardness of the outer core layer 1 mm outside the boundary, and (d) represent the JIS-C surface hardness of the outer core layer, the value (c)-(b) is in a range of from −15 to 10 and the value (d)-(b) is in a range of from −10 to 20, and the inner cover layer has a thickness of from 0.8 mm to 3.0 mm and a Shore D hardness of from 50 to 80, and the outer cover layer has a Shore D hardness of from 35 to 60, which is lower than the Shore D hardness of the inner cover layer.